WO2002069448A1

WO2002069448A1 - Antenna device

Info

Publication number: WO2002069448A1
Application number: PCT/JP2001/001419
Authority: WO
Inventors: Masataka Ohtsuka; Isamu Chiba; Shuji Urasaki
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2001-02-26
Filing date: 2001-02-26
Publication date: 2002-09-06
Also published as: US6707433B2; US20030090433A1; JPWO2002069448A1; EP1365476A4; JP4541643B2; EP1365476A1

Abstract

A plurality of concentric array antennas of different radii are arranged on the same plane. Each concentric array antenna includes a plurality of antenna elements arranged in a circle. A majority of the concentric array antennas are arranged at regular intervals of d, whereas the other concentric array antennas are arranged at intervals of d ± (0. 4-0.6)d. The side lobe of a wide angle can be reduced by changing the radii of some of the concentric circles by ±0.4-0.6d.

Description

Description Antenna device Technical field

The present invention relates to an antenna device that forms a beam by arranging a plurality of element antennas in communication or radar, for example. Background art

FIG. 12 is a diagram showing a conventional antenna device disclosed in, for example, JP-A-7-28817. In FIG. 12, 1 is an element antenna arranged on a plane, and 2 is a concentric circle on which a plurality of element antennas 1 are arranged. Feeding means for adjusting the excitation amplitude and the excitation phase is connected to each element antenna 1. Next, the operation of the above-described conventional antenna device will be described. By adjusting the excitation amplitude and the excitation phase of each element antenna 1 by the feeding means, the present antenna device can obtain desired radiation characteristics. FIG. 13 is a diagram showing another conventional antenna device in ττ; 5 in, for example, pp. 2032-2035, ⁵ Design of low sidelobe circular ring arrays by element radius optimization of 1999 IEEE AP-S. This figure shows an element antenna arrangement in an array antenna in which element antennas 1 are arranged in concentric circles 2. In addition, 4 is a coordinate. In FIG. 13, the table showing the intervals between the concentric circles represents the intervals between the concentric circles 2 in wavelength units. In the same table, the right column shows the case where the concentric circles 2 are arranged at equal intervals, and the left column shows the case where the interval of the concentric circles 2 is adjusted to reduce the number of cyclodes Next, the operation of another conventional antenna device will be described. In other conventional antenna devices, side lobes are reduced by adjusting the interval between concentric circles 2. As a method, a desired radiation pattern is defined, and the radius of the concentric circle 2 is sequentially determined from the inside so as to approximate the desired radiation pattern. However, in order to avoid the quasi-grating lobe described below, the interval between each concentric circle 2 is limited to one wavelength or less. In the above document, when the intervals of the concentric circles are equidistant, the side opening level near the main beam, which was 17.7 dB, was changed when the interval of the concentric circles was adjusted. , —27.4 dB. In an array antenna, it is common to arrange the element antennas in a square array or a triangular array in order to easily configure a feed system. In this square array or triangular array, if the element antenna spacing (hereinafter, element spacing) is widened in order to reduce the number of element antennas, grating lobes having a level substantially equal to that of the main lobe are generated, and radiation in unnecessary directions and the like are generated. Problems arise. On the other hand, the concentric arrangement as in the above-described conventional example has an advantage that a clear grating lobe does not occur even if the element interval is widened. However, even in this concentric arrangement, if the element spacing is widened, sidelobes having a certain level of repelling which can be called a quasi-grating lobe at a wide angle are generated, which may cause a problem in suppressing unnecessary radiation. Fig. 11 (a) shows an example. Fig. 11 (a) is a diagram showing the radiation pattern (radiation characteristics) of an array antenna in which 18 concentric circles are arranged at equal intervals. The element antennas 1 are arranged relatively densely on the circumference of each concentric circle 2 to prevent the occurrence of a high side rope by increasing the element spacing in the circumferential direction. The element intervals along the circumferential direction of all concentric circles 2 are equal, and all element antennas 1 have the same amplitude. The horizontal axis u in FIG. 11A represents the u coordinate (detailed in the Example section) corresponding to the wave number space, and the main beam is configured when u = 0. As the interval between the concentric circles 2 increases, the visible range in which the radiation pattern appears in real space increases. For example, when the main beam is in the zenith direction perpendicular to the antenna plane, when the interval between concentric circles 2 is 1λ (λ: wavelength), 0≤u ^ 6.28, and the interval between concentric circles 2 is 2 In the case of, the area of 0≤u ≤12.5.57 becomes the radiation pattern in the real space. As can be seen from FIG. 11 (a), when the interval between the concentric circles 2 is larger than about one person, a relatively large sidelobe of the level of 120 dB appears at a wide angle. The appearance of the sidelobe depends on the interval between the concentric circles 2. When the main beam is scanned at a wide angle, even the interval between the concentric circles 2 smaller than one person appears in the real space. Also, this wide-angle side lobe level does not change much even if the number of concentric circles 2 increases, and is about 120 dB when the amplitude distribution of the aperture is uniform. As described above, the conventional equidistant concentric array has a problem that if the interval between the concentric circles 2 is increased in order to reduce the number of element antennas 1 and the like, a high-level wide-angle sidelobe is generated. Also, in the case where the interval between the concentric circles 2 is narrow, as described in the other conventional antenna devices, a method for reducing the side lobe by adjusting the interval between the concentric circles 2 has been described. However, no effective method has been clarified when the interval between the concentric circles 2 is more than one. Disclosure of the invention

The present invention has been made in order to solve the above-described problems, and has as its object to provide an antenna device that can suppress the above-described unnecessary wide-side lobe when the interval between concentric circles is widened. The antenna device according to claim 1 of the present invention has different radii on the same plane. A plurality of concentric array antennas, wherein each concentric array antenna has a plurality of element antennas arranged in a circumferential direction, and among the plurality of concentric array antennas, most of the concentric array antennas are arranged at equal intervals d, Of the plurality of concentric array antennas, the remaining concentric array antennas are arranged at an interval of d soil (0.4 to 0.6) d. An antenna device according to a second aspect of the present invention is the antenna device according to the first aspect, wherein an interval between the plurality of concentric array antennas is one or more wavelengths. An antenna device according to claim 3 of the present invention includes a plurality of concentric array antennas having different radii on the same plane, and each concentric array antenna has a plurality of element antennas arranged in a circumferential direction, The plurality of concentric array antennas are divided into a set including four consecutive concentric array antennas, and one concentric array antenna among the four concentric array antennas included in each set is The remaining three concentric array antennas of each set are arranged at an equal interval d, and are arranged at intervals d (0.4 to 0.6) d. An antenna device according to a fourth aspect of the present invention is the antenna device according to the third aspect, wherein an interval between the plurality of concentric array antennas is one or more wavelengths. The antenna device according to claim 5 of the present invention is characterized in that a plurality of element antennas are arranged at equal intervals in a circumferential direction, a radius coefficient is L _n (n is an integer), and a reference interval of the concentric array antenna is d. a _n = L and the first concentric array antenna having _n · d, a plurality of antenna elements are arranged at equal intervals in the circumferential direction, the radius _{_{a n + 1 = L n +}} 1 · d workers (0.4 to 0. 6) A second concentric array antenna having d is provided. An antenna device according to a sixth aspect of the present invention is the antenna device according to the fifth aspect, wherein an interval between the first and second concentric array antennas is one or more wavelengths. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a configuration of an antenna device according to Embodiment 1 of the present invention,

FIG. 2 is a diagram showing an element antenna arrangement of a concentric array antenna according to Embodiment 1 of the present invention,

FIG. 3 is a diagram for explaining the radiation characteristics of the antenna device according to the first embodiment of the present invention in a wave number space.

Fig. 4 is a diagram showing the individual radiation characteristics of concentric circles with radius coefficients L _n = l, 3, 5, and 10 in a concentric array antenna.

FIG. 5 is a diagram showing the radiation characteristics of the concentric array antenna separately. FIG. 6 is a diagram showing the radius coefficient according to the first embodiment of the present invention.

In the case of 8, a diagram showing the radiation characteristics of the entire array in a case where the radius coefficient is 1 ^ = 7 and L ₂ = 7.5, FIG. 7 is a diagram showing the configuration of the antenna device according to the second embodiment of the present invention,

FIG. 8 is a diagram showing a combined radiation characteristic with a radius coefficient of 1 ^ = 7 and L ₂ = 8.44 and a combined radiation characteristic with a radius coefficient of L ₃ = 9 and L ₄ = 10 according to the second embodiment of the present invention. ,

FIG. 9 shows the composite radiation characteristics when the radius coefficients L _{1 =} 7, L ₂ = 8, L ₃ = 9s and L ₄ = 10 according to the second embodiment of the present invention, and the radius coefficients L _{1 =} 7, L ₂ = 8.44, a diagram showing the combined radiation characteristics when L ₃ = 9 and L ₄ = l 0,

FIG. 10 is a diagram showing a configuration of an antenna device according to Embodiment 3 of the present invention,

Fig. 11 shows the combined radiation characteristics of the equally spaced concentric array (18 concentric circles) (conventional example) and the combined radiation characteristics of the irregularly spaced concentric array (18 concentric circles) (Example 3). FIG. 2 is a diagram showing a configuration of an antenna device,

FIG. 13 is a diagram showing a configuration of another conventional antenna device. BEST MODE FOR CARRYING OUT THE INVENTION

Example 1.

First Embodiment An antenna device according to a first embodiment of the present invention will be described with reference to the drawings.

. FIG. 1 is a diagram illustrating a configuration of the antenna device according to the first embodiment of the present invention. Note that

In each drawing, the same reference numerals indicate the same or corresponding parts. In FIG. 1, 1 is an antenna element, and 2 is a concentric circle in which a plurality of antenna elements 1 are arranged. Here, first, the operation of the array antenna in which the element antenna 1 is arranged on the concentric circle 2 will be described, and the effect of the first embodiment will be clarified. FIG. 2 is a diagram showing an element antenna arrangement of a concentric array antenna. In FIG. 2, 1 is an antenna element, 2 is a concentric circle, 3 is an interval between the element antennas 1 along the circumferential direction of the concentric circle 2, and 4 is a coordinate. FIG. 3 is a diagram for explaining radiation characteristics of the antenna device in a wave number space. In FIG. 3, reference numeral 5 denotes wave number space coordinates, and reference numeral 6 denotes a visible region. Next, the structure of the present antenna device will be described. As shown in FIG. 2, the present antenna device has a plurality of element antennas 1 arranged on a plurality of concentric circles 2 assumed on an XY plane of coordinates 4. As shown in Fig. 2 (b), concentric circles 2 are numbered sequentially from the inside (1, 2, 3, ..., η, ..., Ν), and the total number is Ν. Also, the η th same Kokoroen second radius is set to a _n, the number of antenna elements located on the n-th concentric circle 2, M _n pieces. Within one concentric circle 2, the element antennas 1 are arranged at equal intervals in the circumferential direction of the concentric circle 2, and all the element antennas 1 on the nth concentric circle 2 have the same excitation amplitude. _Let this be En. Further, in the n-th concentric ¥ 2, antenna elements 1 to position rotated by an angle delta _eta from the X-axis of the coordinate 4 is assumed to continue being placed. Next, the operation of the present antenna device will be described. The present antenna device obtains desired radiation characteristics by giving the element antenna 1 a predetermined excitation amplitude and excitation phase. In the first embodiment, a case is considered in which an excitation phase is given in a desired direction (ø, _Φΰ ) so that the radiation phases of the element antennas 1 are co-phase. Assuming that the angle on the X-y plane of the _mn- th element antenna 1 on the η-th concentric circle 2, counting from the X-axis, is izTm _n and the wave number in free space is k, the radiation characteristics of this antenna : F (θ, φ) is expressed by the following equation (1). Ιθ, φ) = y Ε _η ^ exp jk- α _η | (sin θ cos φ cos φ_ '. + Sin0sm sm ^ _m I

-(sin0 _o cos ^ ₀ cos + sin ^ ₀ sin sin)}] where E. „=) E„ 'M „

… Equation (1) When the above equation (1) is expressed in a wavenumber space with s in (cos and s in6> s in0 orthogonal axes), the following equation (2) is obtained. 2) In, J _n is an nth-order Bessel function of the first kind.

Where yo = (sin0∞s ー sui0 _o ∞s ^> _o ) + (sin 0 sin-sin θ ₀ sin φ ₀ )

• · Expression (2) From the above equation (2), the radiation properties of the Fourier space, as shown in FIG. 3, beam direction _{(s in0.coss in6> .s in 0} ) the distance from p is Oite sine the constant circumference It can be seen that the amplitude changes like a circle. In Fig. 3, the radiation pattern that appears in the actual physical space is within the circumference at a distance of 1 from the origin of wavenumber space coordinate 5 (visible range 6). Further, from the above equation (2), the single underline having the 0th-order Bessel function of the first kind contributes to the main beam (position of = 0) and the sidelobe (region of> ()). Since the heavy underline is formed by a first-order Beth-cell function of first order or higher with no value at ρ = 0, it can be seen that it contributes only to the side lobes with p> 0.

The Bessel function of the first kind J _n (X) of the first order or higher has a very small value at about x = 0 to _n , and changes sinusoidally at X larger than this. Therefore, if the term of q = 1 in the double underlined part of the equation (2) is sufficiently small within the visible range 6, the term of q> 0 can be ignored, and the entire double underlined part becomes small. That is, if the number of element antennas _Mn on each concentric circle 2 is large to some extent, the double underline of Equation (2) can be ignored in the visible range 6, and the radiation characteristics can be evaluated only with the single underline. In this case, the radiation pattern eliminates depends circumferentially variable wavenumber space, beam direction (si n6> .c 0 s. , Si n0.sin 0) distance P from the at constant circumferential It has a constant amplitude. That is, it has a radiation characteristic that is rotationally symmetric about the beam direction in the wave number space. Here, the reference interval of the concentric circles 2 and d, represents the n-th radius of the concentric circles 2 and a _{_n} = L _n · d. Note that L _n is a radius coefficient. If the double underlined part of the above equation (2) is omitted, the radiation characteristic is expressed as the following equation (3).

^ E, M _n- {j ₀ (k'L _n -dp)}

• Eq. (3) This Eq. (3) is expressed in u-coordinate in wavenumber space. As described above, the radiation characteristics in Fig. 11 (a) are as follows: all concentric circles 2 have the same spacing (L _n = n), and all element antennas 1 have the same amplitude (E _n = l). This shows a case where circumferential element intervals on all concentric circles 2 are equal (M _n ∞L _n ). Next, in FIG. 11A, the reason why a large side lobe occurs near the coordinate u = 6.3 or u = 12.6 in the wave number space will be described. FIG. 4 shows individual radiation characteristics at concentric circles 2 with radius coefficients L _n = l, 3, 5, and 10 in the concentric array antenna having the radiation characteristics of FIG. 11 (a). The calculation is based on equation (3). As can be seen from the phase relationship, the amplitude on the vertical axis is represented by the electric field exact value. As can be seen from FIG. 4, when the radii of all the concentric circles 2 are radius coefficients L _n = m and m is an integer (this includes the case where the intervals of all the concentric circles 2 are equal.) The radiation characteristics of 2 become almost in-phase near the wave number space coordinate u = 6.3 or u = 12.6. This results in a large cycloid. Next, a specific example of the first embodiment and its effects will be described. For simplicity, consider a concentric array consisting of two concentric circles 2. The radius coefficient is 1 ^ in equation (3). = 7 and L ₂ = 8. Figure 5 shows the radiation characteristics of this concentric array separately. As described above, since the radius coefficient L _n = m and m is an integer, as in Fig. 4, the coordinates of the radius coefficient are almost in phase near u = 6.3 or u = 12.6. It has become. Strictly speaking, a concentric circle with a radius coefficient of 1 ^ = 7 has a peak at u = 6.4. Here, if the value of the radius coefficient L ₂ is adjusted so that the valley of the concentric circle 2 of the radius coefficient L ₂ is superimposed on the peak of the coordinate u = 6.4 in the concentric circle 2 of the radius coefficient L, 2 7 The side lobes near the coordinate 11 = 6.3 in both composite patterns should attenuate. Since the valley of the concentric circle 2 with the radius coefficient L ₂ = 8 is at the coordinate u = 6, a new radius coefficient L ₂ = 8x6 / 6. 4 = 7.5. If in FIGS. 6 (a) of the radius coefficient _{_{L 1 = 7, L 2 =}} 8, showing the radiation characteristics of the entire array in the case of the radial coefficient _{_{L 1 = 7, L 2 =}} 7. 5 in FIG. (B). From FIGS. 6 (a) and (b), it can be seen that by adjusting the radius of the concentric circle 2 having the radius coefficient L ₂ , the sidelobe at a wide angle (especially u> 4) is reduced. By adjusting the radius of the concentric circles 2 adjacent to each other in this manner, it is possible to reduce the side ropes at a u-wide angle. Since this method superimposes adjacent peaks and valleys, the variation of the radius coefficient L ₂ is approximately ± 0.4 to 0.6. Even in the case of a larger number of concentric circles 2, wide-angle side drops can be reduced by adjusting the radius of some concentric circles 2 in the same manner. As described above, in the first embodiment, by changing some radii of a plurality of concentric circles 2 by ± 0.4 to 0.6d (d: reference interval of the concentric circles 2), a wide-angle side port is provided. -Has the effect of reducing the number of Example 2.

Embodiment 2 An antenna device according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 7 is a diagram illustrating a configuration of the antenna device according to the second embodiment of the present invention. In FIG. 7, 1 is an antenna element, and 2 is a concentric circle in which a plurality of antenna elements 1 are arranged. Here, a concentric array consisting of four concentric circles 2 is considered. Initially, the radius coefficients are 1 ^ = 7, L ₂ = 8, _S L ₃ = 9, and L ₄ = 10. Here, the radius of the concentric circle ₂ with the radius coefficient L ₂ is adjusted, and L ₂

Of u = 6. And 4 peaks, which was so as to superimpose the trough of u = 6. 75 of L ₂ = 8, the radius coefficient L ₂ = 8 X 6. 75/6. As 4 = 8.44 I'm asking. This and Kino radius factor _{1 ^ = 7, L 2 =} 8. Synthesis radiation characteristic of 44 in FIG. 8 (a), its radius coefficient _{_{L 3 = 9, L 4 =}} 10 in FIG. (B) Show. The radiation characteristics in Fig. 6 (a) and Figs. 8 (a) and (b) are all waves on the u-axis in wavenumber space, but here we focus on the normal lines. And Figure 6 showing the radiation characteristics of the radius coefficient L丄= 7 and L ₂ = 8 (a), than that of FIG. 8 showing the radiation characteristics of the radius coefficient L ₃ = 9 and L ₄ = 10 (b), Law絡線Peaks and valleys almost correspond to each other. This is the radius factor

If the radius of the concentric circle changes at an equal interval to 10, it means that the sidelobe tends to increase at a specific position. In contrast, FIG. 8 shows the synthesis radiation characteristics of radial coefficient _{1 ^ = 7, L 2 =} 8. 44 (a) is a law絡線beaks and valleys become Irechigai generally to FIG. 8 (b) I have. Therefore, it is expected that side lobes will be reduced in the radiation characteristics that combine Figs. 8 (a) and 8 (b). The radius coefficient _{LM = 7, L 2 = 8} , L 3 = 9 S L 4 = 1 0, the radius coefficient _{_{L 1 = 7, L 2 =}} 8. 44, the synthesis of the case of _{_{L 3 = 9, L 4 =}} 10 The radiation characteristics are shown in Fig. 9 (a) and (b), respectively. In the latter radiation characteristic, the sidelobe is reduced at wide angle (especially, near u = 6.3). As described above, in the second embodiment, of the two concentric circles 2, the combination of the concentric circles 2 in which one radius is adjusted by ± 0.4 to 0.6 d and the concentric circles 2 in which both are not adjusted are set. In other words, by adjusting the radius of only one of the four concentric circles ± 0.4 to 0.6d, the wide-angle side rope can be reduced. Example 3.

Third Embodiment An antenna device according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a diagram illustrating the configuration of the antenna device according to the third embodiment of the present invention. In FIG. 10, 1 is an antenna element, and 2 is a concentric circle in which a plurality of antenna elements 1 are arranged. Reference numeral 7 denotes a set of four concentric circles 2 described below. In Example 2 described above, the sidelobes were reduced by four concentric circles 2.However, in an array antenna composed of a larger number of concentric circles 2, the concentric circles 2 were grouped into groups of four, each having a set 7. By adjusting the radius of one concentric circle 2 in the set 7 by ± 0.4 to 0.6 d, the number of sides can be reduced. In FIG. 10, X and Y are values normalized by the reference interval d of the concentric circle 2. Example 3 is composed of 18 concentric circles 2 and, apart from the concentric circles of n = 1 and 2, which have a small contribution to the radiation characteristics, n = 3 to 6, n = 7 to 10, and n = ll to 14 The method of the second embodiment is applied to a set 7 of concentric circles 2 of n = 15 to 18 (n represents a position from the inside of the concentric circle 2). In other words, L ₄ = 4.43, L ₈ = 8.44, L ₁₂ = 12.47, L ₁₆ = 16.50, and L _n = n in other cases. FIG. 11 (b) is a diagram showing the combined radiation characteristics of the entire unequally spaced concentric array. For comparison, Fig. 11 (a) shows the radiation characteristics when the above adjustment is not performed, that is, when the intervals between all the concentric circles 2 are equal (L _n = n in all the concentric circles 2). 11 (a) and 11 (b), the vertical axis is displayed in dB. From FIGS. 11 (a) and 11 (b), the wide-angle sidelobe is reduced by the method of the third embodiment, and in particular, a reduction of about 5 dB is obtained near the coordinate u = 6.3. You can see that. That is, the maximum wide-angle sidelobe level has been reduced by 5 dB. As described above, the method of the third embodiment has the effect of reducing the wide-angle sidelobe level even in an array antenna having a larger number of concentric circles 2. As already mentioned, if the concentric spacing of concentric arrays is increased for the purpose of reducing the number of element antennas, etc., even if the grating lobes seen in the triangular array or square array do not appear, the higher level side There was a problem that lobes occurred. Each of the above-described embodiments shows a method of lowering the side opening in this concentric arrangement, and is particularly effective in the case where the concentric interval is one wavelength or more. large. It also has the effect of reducing the number of element antennas by increasing the concentric intervals. Further, in a phased array antenna or the like in which an expensive module is connected for each element antenna, the effect of reducing the cost according to the present invention is great.

Claims

The scope of the claims

1. Provide a plurality of concentric array antennas having different radii on the same plane,

In each of the concentric array antennas, a plurality of element antennas are arranged in a circumferential direction, and among the plurality of concentric array antennas, most of the concentric array antennas are arranged at equal intervals d,

Of the plurality of concentric array antennas, the remaining concentric array antennas are arranged at an interval of d (0.4 to 0.6) d

Antenna device.

2. The interval between the plurality of concentric antennas is at least one wavelength

The andena device according to claim 1.

3. A plurality of concentric array antennas having different radii on the same plane,

In each concentric array antenna, a plurality of element antennas are arranged in a circumferential direction, and the plurality of concentric array antennas are divided into a set including four continuous concentric array antennas, and four concentric array antennas are included in each set. Of the concentric array antennas are arranged at a distance d (0.4 to 0.6) d,

The remaining three concentric array antennas of each set are arranged at equal intervals d.

4. The interval between the plurality of concentric array antennas is at least one wavelength

The antenna device according to claim 3.

5. Multiple antenna elements are arranged at equal intervals in the circumferential direction, the radial coefficient L _n (n is an integer), when a reference interval of the concentric circles array antenna is d, the having a radius a _{_n} = L _n 'd 1 concentric array antenna, A plurality of element antennas are arranged at regular intervals in the circumferential direction, and a second concentric array antenna having a radius a _{n + 1} = L _{n + 1} · d (0.4 to 0.6) d

An antenna device comprising:

6. The antenna device according to claim 5, wherein a distance between the first and second concentric array antennas is one or more wavelengths.